The present invention relates to shift lock units for shift lever devices for use in automatic transmissions.
In a growing tendency of the wide use of gate-type multistage transmissions, JP-A 7-119813 proposes a shift lever device which includes a lock unit for ensuring shift lock from the parking (P) or neutral (N) range to the reverse (R) range to prevent careless shift operation of the transmission.
The reference shows, in the first embodiment, a lock unit comprising a V-shaped stopper which has P and N engagements engageable with the P and N ranges of a gate for a shift lever arranged to be swingable in the longitudinal and cross directions of a vehicular body. The stopper is rotated by a solenoid or actuator operated in accordance with brake operation or achievement of a given vehicular speed, obtaining shift lock.
The reference shows, in the second embodiment, a lock unit comprising a stopper which includes two links so that P and N engagements are movable close to and apart from each other, solving a problem of the first embodiment due to movement of the P and N engagements in the same direction.
However, with the lock unit as described in the first embodiment, continuous operation of the solenoid during vehicular cruising puts the N engagement in the N range to achieve N-range shift lock, resulting in shortened reliability with regard to breakdown, etc. of the unit. Moreover, shift lock cannot be obtained when the electric system is break down. On the other hand, with the lock unit as described in the second embodiment, the lock unit can solve the problem of the first embodiment by using the stopper including two links, which means, however, increased number of parts, resulting in lowering of the operating accuracy of the unit.
It is, therefore, an object of the present invention to provide shift lock units for shift lever devices, which secure high reliability with simple construction.